I'm the only person I've encountered that naturally runs on a 25 hour clock. I get the same amount of sleep per day (~8 hours) but I follow it with 17 hours of wakefulness so my clock moves forward by an hour every day. To my knowledge there are no adverse health effects, but it's certainly out of the ordinary. I often wonder if more people are like me since sleep problems are so common, but they cannot follow their…
I have it too. Have since childhood.
There seem to be various incarnations of it: it's pretty common among blind people, though not all have it.
Some people just seem to have a really long day, 26+ hours, so that they need extreme light exposure to entrain to the sun's rhythm.
I tried that, and apparently it was something else - I suspect a defect in the suprachiasmatic nucleus (https://en.wikipedia.org/wiki/Suprachiasmatic_nucleus), which is a part of the brain responsible from interpreting the signals from the eye that keeps the daily clock in sync.
I've mostly fixed it using the Ketogenic Diet (https://en.wikipedia.org/wiki/Ketogenic_diet), which tells me it has something to do with the sugar metabolism in the brain. Because that's what the ketogenic diet addresses eg. in epileptics.
Ever since finding out I had this "incurable" condition and fixing it within 3-4 days of keto, I've been just a regular night owl. I like to go to bed at 2am and wake up around 10am, though I have to make due with 12-8 for work :-/ It's not the same though. In my experience, sleeping at the correct time makes an enormous difference.
I've been "symptom free" from Non24 for almost 3 years now using keto, and I know of 2 other people that have had success.
Should your SCN not be the problem, but you simply have an extremely long circadian rhythm, you can try extreme morning light exposure. This giant article explains tons about DSPS and what he calls the "farmer's lifestyle": https://www.supermemo.com/en/articles/sleep#farmers_lifestyl.... (He's wrong about Non24 always being an extreme form of DSPS - it does exist).
It is worth experimenting months at a time and solving this. You'll spend 1/3 of the rest of your life sleeping, finding out how your body wants to sleep is a huge investment. I found out in my 30s that I had an "incurable condition" and had it accidentally fixed a year later.